In cooling of an air conditioner or a thermal grid system or intake air cooling of a gas turbine (a gas turbine device), heat is transported by circulating a heat transport medium having a heat storage property through a pipeline (pipe). As the heat transport medium, water or brine for utilizing sensible heat is known, and water is widely used from the viewpoint of low cost and high safety. However, for sensible heat transport with the heat transport medium such as water, the heat transport medium has a small heat capacity, and a large carrying power (a huge pump) is required to carry a large quantity of the heat transport medium. In a wide area thermal grid, the problem with use of sensible heat transport is a low energy efficiency. To solve this problem, it has also been studied a method of utilizing latent heat associated with a phase change of a latent heat storage material as the heat transport medium. For latent heat transport with the latent heat storage material, the latent heat storage material, which has a large heat capacity, prevents the drop in temperature over long distances of transportation and also cuts down a carrying power. Unfortunately, the latent heat storage material solidifies by phase change to block a pipeline, and thus the latent heat storage material cannot be utilized as it is. To solve this problem, it has been reported a method of utilizing a microencapsulated latent heat storage material. According to this method, heat transport (heat exchange) using a latent heat of a latent heat storage material and a sensible heat of a fluid is performed by circulating the fluid containing microcapsules filled with the latent heat storage material.
Japanese Patent Application Laid-Open Publication No. 5-215369 (JP-5-215369A, Patent Document 1) discloses a method of cooling or heating an object by circulating, in a closed circuit between a cooling device or a heating device and a heat exchanger, a heating medium cooled or heated with the cooling device or the heating device to cool or heat the heat exchanger; the heating medium is a mixture of a large number of resin microcapsules containing a heat storage material such as paraffin, and water or brine.
WO2015/025529 (Patent Document 2) discloses a latent heat transport material microencapsulated in a hard shell (or a hard shell microencapsulated latent heat transport material), as a heat medium of a heat transport device that recovers high-temperature waste heat and transports the waste heat to a place where heat is necessary; the hard shell microencapsulated latent heat transport material comprises a phase change material that absorbs or releases a latent heat in response to temperature changes, and non-porous hollow silica particles enclosing the phase change material.
Japanese Patent Application Laid-Open Publication No. 2000-161082 (JP-2000-161082A, Patent Document 3) discloses an intake air cooling device for a gas turbine; the intake air cooling device comprises an intake port, an intake path from the intake port to the gas turbine, and an ice thermal storage tank coupled with the intake path, the ice thermal storage tank having a large number of heat storage capsules, each having a solid periphery, arranged leaving ventilation gaps, and the ice thermal storage tank being configured to directly contact at least a portion of an intake air with the peripheries of the heat storage capsules across the ice thermal storage tank to cool the portion of the intake air. This document discloses that capsules enclosing a heat storage material that undergoes solid-liquid change in a temperature range of 0 to 20° C. are used as the heat storage capsules.
Unfortunately, for these heat-transport media, which have a latent heat transport material microencapsulated therein, the microcapsules would be broken with long-term use or by an external stress (e.g., a mechanical stress such as a shearing force in pumping), resulting in aggregation of the latent heat storage material which would solidify in a pipeline inside a cooling device to block the pipeline. If the shell of the microcapsules is strengthened or thickened to avoid the microcapsules from broken, the microcapsules would decrease the heat exchange efficiency. Thus, there is a trade-off relationship between the heat conversion efficiency and the stability.
Japanese Patent Application Laid-Open Publication No. 4-222894 (JP-4-222894A, Patent Document 4) discloses a medium for heat-transfer system; the medium comprises a continuous phase that is liquid at least in use and a dispersed phase having an average particle size of 0.2 to 50 μm and exclusively consisting of a heat storage material having a melting point higher than the continuous phase. This document discloses the following: if the medium is in a suspension state having the dispersed phase in a solid state, the average particle size of the dispersed phase is 0.2 to 50 μm and thus the medium is transferred while maintaining an excellent flowability; and if the continuous phase is formed of a poly (ethylene glycol) and/or a poly(propylene glycol), the continuous phase has a thickening action to prevent the aggregation of the dispersed phases.
Japanese Patent No. 3641362 (JP-3641362B, Patent Document 5) discloses a cold storage agent of a cold body to be used for an air conditioner (such as an air-cooling apparatus) or a cooling device for food or other products; the cold storage agent is an aqueous solution containing an inclusion hydrate producing substance having a concentration less than a concentration providing a congruent melting point of an inclusion hydrate, and is configured to produce an inclusion hydrate by cooling and give a slurry.
Unfortunately, for the emulsion or suspension and the slurry, the dispersed phase is exposed in the fluid and thus may be aggregated. Further, for the slurry, the dissolved latent heat storage material is essentially unutilized, decreasing the heat conversion efficiency.
Japanese Examined Patent Application Publication No. 5-41678 (JP-5-41678B, Patent Document 6) discloses a heat storage composition containing a phase change material and a polyolefin-based carrier material having the phase change material incorporated therein; the phase change material is a substance which has such a compatibility that the phase change material is dispersed in the carrier material and does not substantially exude out of the system, and the phase change material is at least one substance selected from the group consisting of a crystalline straight-chain alkyl hydrocarbon, a crystalline fatty acid, a crystalline fatty acid ester, a crystalline alicyclic hydrocarbon, and a crystalline aromatic hydrocarbon. This document discloses that the polyolefin-based carrier material is preferably a crosslinked polyolefin. This document also discloses that the composition is incorporated in gypsum or concrete to be utilized for a building material.
Japanese Patent Application Laid-Open Publication (Translation of PCT Application) No. 2002-523719 (JP-2002-523719A, Patent Document 7) discloses a latent heat body having a paraffin-based latent heat storage material and a carrier material having a holding space in which the paraffin-based latent heat storage material is absorbed; the carrier material has a capillary holding space formed thereinside for the latent heat storage material, and the carrier material is a mineral substance with an open capillary pore structure. This document discloses that the latent heat body is utilizable for, e.g., a building material (e.g., a heat storage wall, a roof, and a floor storage heating system), a warming plate for rice, a radiator disposed between a bare floor and a covering in an electric floor heating, and a transport container for maintaining an article stored in the container at a constant temperature during transport. This document also discloses that the carrier material having a holding space includes a gypsum material, a clay material, a calcareous sandstone, a siliceous earth, a wood fiber, and a cardboard.
However, Patent Documents 6 and 7 fail to disclose use (heat transport) of a latent heat storage material in a fluid. Incidentally, these compositions or latent heat bodies have no shape recoverability. If these compositions or latent heat bodies are used as a heat transport medium, the heat transport medium may be broken by an external load stress to exude the latent heat storage material. The exuded latent heat storage material would gradually aggregate without reabsorption to the carrier material, which fails to restore a shape thereof, and the aggregation would cause blockage of a pipeline by solidification.